Semi-dynamic Model Research Articles

In vitro simulated study of macronutrient digestion in complex food using digestive enzyme supplement

Digestive enzymes secreted by the body are vital for digestion and nutrient absorption. Enzyme supplements are commonly used to support them in achieving optimal digestion. Herein, the efficacy of digestive enzyme supplement (DigeSEB Super) in digestion of complex food was assessed using INFOGEST simulated static and modified semi-dynamic in vitro digestion models. Digestive enzyme supplement was found to assist the endogenous digestive enzymes to disintegrate the food matrix. Hence, it reduced the viscosity of the gastric digesta by 2.75 fold (p = 0.04) compared to the control digestion (only endogenous digestive enzymes) during the first hour of digestion. Similarly, enzyme supplement showed statistically higher release of reducing sugars in the gastric digestion (p ≤ 0.05) indicating improved digestion of carbohydrates. Further, digestion of proteins and fats was also improved in the presence of enzyme supplement. The kinetic aspects of the semi-dynamic model (transient nature of gastric secretions and gradual acidification) was found to alter the macronutrient digestion compared to the static digestion. Thus, semi-dynamic model should be preferred for the in vitro studies. Overall, current study demonstrated the potential of a digestive enzyme supplement to improve digestion by aiding digestive action of the endogenous enzymes.

Extension of a static into a semi-dynamic traffic assignment model with strict capacity constraints

To improve the accuracy of large-scale strategic transport models in congested conditions, this paper presents a straightforward extension of a static capacity-constrained traffic assignment model into a semi-dynamic version. The semi-dynamic model is more accurate than its static counterpart as it relaxes the empty network assumption, but, unlike its dynamic counterpart, maintains the stability and scalability properties required for application in large-scale strategic transport model systems. Applications show that, contrary to static models, semi-dynamic queue sizes and delays are very similar to dynamic outcomes, whereas only the congestion patterns differ due to the omission of spillback. The static and semi-dynamic models are able to reach user equilibrium conditions, whereas the dynamic model cannot. On a real-world transport model, the static model omits up to 76% of collective losses. It is therefore very likely that the empty network assumption influences (policy) decisions based on static model outcomes.

Impact of food viscosity on in vitro gastric emptying using dynamic and semi-dynamic models

Viscosity has been shown to affect food breakdown and nutrient release in the gastrointestinal tract, and the subsequent postprandial glycaemic response and satiety. However, the correlation between food viscosity and gastric emptying is not fully understood. This study investigated the in vitro gastric emptying behavior of peanut butter with different viscosities using semi-dynamic and the artificial gastric digestive system (AGDS) models. Results from both digestion models showed that high viscosity peanut butter had a slower pH decrease, higher buffering capacity, slower phase separation of gastric chyme and less protein hydrolysis and lipid digestion than the control and low viscosity groups. However, the AGDS displayed slower gastric emptying rate, smaller chyme particle size and less proteolysis than the semi-dynamic model, particularly in the high-viscosity group (e.g. ∼60% of gastric emptying rate for AGDS and ∼20% for semi-dynamic model at 120 min), due to the different mechanical shearing forces and gastric emptying patterns in these two models. This study demonstrated the role of food viscosity on the gastric emptying process, and it also suggested that viscosity should be taken into account when designing future functional foods with particular structure.

Modulation of viscosity, microstructure and lipolysis of W/O emulsions by cellulose ethers during in vitro digestion in the dynamic and semi-dynamic gastrointestinal models

In this study, W/O emulsions incorporated with various proportions of two hydrocolloids, namely, methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC), were prepared. The shear viscosity, microstructure, and lipolysis of the W/O emulsions before and during in vitro digestion in the dynamic (DIVHS) and semi-dynamic gastrointestinal models were evaluated and compared. The shear viscosity of both emulsions increased with the addition of MC and HPMC content up to a certain limit (0.5–2%), whereas it significantly decreased at a higher addition level (4%) due to the increased flocculation and coalescence in higher cellulose ethers. The HPMC emulsions (2 wt % in aqueous phases) showed higher viscosity and larger droplet size than the equivalent MC emulsions before and during simulated digestion, accompanied by the lower extent of lipolysis. These results are in line with the formation of a more compact and stronger gel structure in HPMC emulsions, which could retard lipase adsorption at the W–O interface. For both emulsions at the same concentration (40 wt%), a higher extent of free fatty acid (FFA) release was found during digestion in the dynamic system (HPMC ꞊ 62%, MC ꞊ 72%) compared to that in the semi-dynamic model (HPMC ꞊ 58%, MC ꞊ 70%). This behavior was supported by the smaller droplet size of emulsions digesta collected from the dynamic system having a larger surface area. Overall, the present study suggested that the dynamic DIVHS system was more effective in enzymatic hydrolysis of the W/O emulsions investigated than the semi-dynamic model under the current experimental conditions. This work had provided valuable insights into the modulation of the structural and digestive properties of W/O emulsions by the addition of MC and HPMC, which could be meaningful for the development of healthier emulsion-based food products (e.g., margarine and spreads) with reduced lipid digestibility.

Mycotoxin Interactions along the Gastrointestinal Tract: In Vitro Semi-Dynamic Digestion and Static Colonic Fermentation of a Contaminated Meal.

Aflatoxin B1 (AFB1) and ochratoxin A (OTA) naturally co-occur in several foods, but no studies have followed the fate of mycotoxins’ interactions along the gastrointestinal tract using in vitro digestion models. This study used a novel semi-dynamic model that mimics gradual acidification and gastric emptying, coupled with a static colonic fermentation phase, in order to monitor mycotoxins’ bioaccessibility by the oral route. AFB1 and OTA bioaccessibility patterns differed in single or co-exposed scenarios. When co-exposed (MIX meal), AFB1 bioaccessibility at the intestinal level increased by ~16%, while OTA bioaccessibility decreased by ~20%. Additionally, a significant increase was observed in both intestinal cell viability and NO production. With regard to mycotoxin–probiotic interactions, the MIX meal showed a null effect on Lactobacillus and Bifidobacterium strain growth, while isolated AFB1 reduced bacterial growth parameters. These results were confirmed at phylum and family levels using a gut microbiota approach. After colonic fermentation, the fecal supernatant did not trigger the NF-kB activation pathway, indicating reduced toxicity of mycotoxins. In conclusion, if single exposed, AFB1 will have a significant impact on intestinal viability and probiotic growth, while OTA will mostly trigger NO production; in a co-exposure situation, both intestinal viability and inflammation will be affected, but the impact on probiotic growth will be neglected.

Effect of oil droplet size on the gastric digestion of milk protein emulsions using a semi-dynamic gastric model

A small droplet emulsion (SDE) of D4,3 = 0.877 μm and a large droplet emulsion (LDE) of D4,3 = 2.19 μm, containing 3.5 wt% milk protein concentrate and 4.5 wt% sunflower oil, were made. The digestion of the samples was performed using a semi-dynamic model, which simulates the main dynamics of gastric digestion, including gradual acidification, enzyme secretion and gastric emptying. Both SDE and LDE coagulated in 10 min digestion when the pH was ≥5.2. Clots of SDE gradually creamed, but clots of LDE sedimented as shown in light-scattering curves. Confocal images showed a higher inclusion of oil droplets in SDE clots, which later coalesced inside the protein matrix and formed oil pools. Texture analyzer profiles exhibited that clots of LDE were firmer than SDE. The nutrients emptying profile indicated a delay in delivering protein and lipid from SDE digesta while LDE digesta emptied a significantly (P ≤ 0.05) higher amount of protein than SDE at initial gastric emptying points. The absorption of casein micelles to the vast interfacial area of SDE led to the higher association of lipids and proteins, which reduced the clots density and led to the creaming behaviour and late nutrients emptying. The coagulation of casein micelles in LDE formed firm structures that squeezed out soluble proteins and lipids to the serum phase leading to the sedimentation of clots and earlier nutrients emptying. The results shed some light on variations observed in physiological responses in satiety after consuming milk protein emulsions.

Early design phase energy predictions using a semi-dynamic approach as an accurate proxy for dynamic energy simulations

The building sector is well known as one of the significant contributors to climate change. The use of materials and energy are important drivers, both during construction and the whole life cycle. This study is part of a research to improve the Belgian national approach of life cycle environmental assessment for buildings. The current approach focusses mainly on material use, and the operational energy is estimated via the equivalent degree day method assuming a fixed value of 1200 equivalent heating degree days per year. This paper extends this widespread degree day approach to improve its accuracy by including the effect of various parameters (climate, building characteristics, obstructions by the environment, occupant behaviour). Step by step user-friendly input and graphical feedback is moreover considered necessary for designers and has been added. The annual heating energy estimated by our proposed semi-dynamic model has been validated by dynamic energy simulations using EnergyPlus of 8000 randomly generated cases. Both results have been plotted in a 2D graph. The slope of the linear regression through the origin is 0.8955, and the R-square value is 0.9058. Based on this comparison, it is concluded that the semi-dynamic model, with simplified input and fast results, has sufficient accuracy for the first design phases compared to the dynamic model.

Input-Output Table Regionalization and Multiregional Input-Output Model Development Algorithm

The main problems of constructing multiregional input-output (IO) models used for the development of spatial and sectoral long-term national economy forecasts are caused by the absence of proper statistics. Therefore, it is necessary to make up the input-output tables (IOTs) based on a limited set of direct and indirect indicators that measure spatial patterns of production, consumption, capital formation, etc., sufficiently accurate for filling up multiregional IO models. The paper discusses Russian IOT spatial mapping problems and proposes an approach to partial automation of the procedures necessary for regional IOT construction (by federal districts). The regionalization was carried out using a static IO model with the bounding sum control. As a result, a set of consistent regional tables for 2015 was developed, with the eight IOT sum equalling Russia’s IOT. Based on the estimated regional IOTs, a static multiregional input-output model (OMIOM) across federal districts for 2015 was made up. The model allows us to proceed to the follow-up phase, i. e., developing a semi-dynamic model for long-term national economic projection computations

REGIONALIZATION OF INPUT-OUTPUT TABLESAND AS A NECESSARY ELEMENT OF ANALYSIS AND FORECASTING OF THE MODEL

The main problems of constructing models used to develop of spatial and sectoral long-term economic forecasts are due to the lack of direct statistical data in full, i.e. regional tables of distribution of goods and services. Their calculation has to be carried out on the basis of a limited set of direct and indirect indicators that make it possible to determine the spatial structures of production, consumption, accumulation of fixed capital, etc. with an accuracy sufficient for further use in the information content of interregional intersectoral models. The report examines the problems of spatial allocation of the all-Russian table “input-output” and proposes the author's approach to the partial automation of the procedures necessary to construct a set of regional tables (by federal district). Regionalization was carried out using a static interregional intersectoral model with control of bordering outcomes. The result is a set of consistent regional tables as of 2015 - the sum of eight input-output tables exactly matches the all-Russian table. The constructed static multiregional input-output model (OMIOM) across federal districts is necessary for the next stage of work - the development of a semi-dynamic model used to calculate options for long-term national economic forecasts.

Программный и проектный подходы при решении крупномасштабных экологических проблем

The article discusses the federal program “Ecology of the Angara-Yenisei region (AYR)”. The description of the systemic synthesis of different approaches to the assessment of the program of restoration and preservation of the natural complex of the Yenisei, as the skeletal basis of the ecological-assimilation potential of AEP is given. The necessity of taking into account the uncertainty factor when evaluating large-scale environmental projects is substantiated. Purpose of the study. Show that the effects of large-scale projects affect the very scenario of economic development, in this regard, it is incorrect to use the primitive integration of an alternative (strategy) into the same scenario, it is shown that it is necessary to evaluate the “project – scenario” relationship. Materials and methods. The authors propose to use three levels of assessment for evaluating large-scale projects: macro level, meso level and micro level. This classification allows you to gradually reduce the level of uncertainty. The information obtained at the previous level of assessment is the source for the lower level. Results. At the first stage, the judgments of the experts were processed using computer products developed at the IEIE. At the second step, the National Project “Ecology of Russia” was analyzed, consisting of 11 federal projects, and a mathematical model was developed for the multicriteria problem of optimal cost management of the project, taking into account the uncertainty factor. The result of the third step was the creation of a hybrid model for assessing large-scale environmental projects from a logical-heuristic model based on expert information and an economic-mathematical model. Analogs of such models, created with the participation of the authors, work in the evaluation of large-scale railway projects. This refers to a family of semi-dynamic optimization models, which have been tested to varying degrees in solving meso-level problems, both in planned and market economies. Moreover, on the basis of one of the versions of this family, a medical-ecological-economic model was developed, and with its help, a scenario analysis of the development of the subjects of the Asian part of Russia was carried out. Conclusion. The article provides a brief description of the functionality and the need to use the appropriate mathematical and software tools as the stages of large-scale projects progress from concept to implementation.

A waste cryogenic energy assisted freshwater generator for marine applications

The scarcity of freshwater resources in the marine environment drives advancement of conventional desalination technologies. It is appealing to recover waste thermal energy to power desalination process. With the fast expansion of the global fleet of liquefied natural gas (LNG) powered vessels and the number of LNG terminals, it is envisaged that LNG cryogenic energy becomes an important form of waste thermal energy apart from engine exhaust. A freshwater generator assisted by LNG cryogenic energy is proposed and investigated in the paper. A semi-dynamic model of the proposed system is used to predict performance and optimal parameters. Feed-in seawater, cooling medium, and configurations of the evaporator and the condenser are three key factors to influence the freshwater production rate and required cryogenic energy. The optimal design is able to provide 1021.7 kg/h freshwater from feed-in seawater of 1296 kg/h and LNG evaporation of 3150 kg/h. A scenario study on an LNG powered cruise ferry predicted that freshwater of 16,991 kg is generated in the 48-hour voyage with the fluctuating LNG cryogenic energy from evaporation, which varies between 212 kW and 973 kW.

Dynamical effects in the integrated X-ray scattering intensity from imperfect crystals in Bragg diffraction geometry. I. Semi-dynamical model.

The analytical expressions for the coherent and diffuse components of the integrated reflection coefficient are considered in the case of asymmetric Bragg diffraction geometry for a single crystal of arbitrary thickness, which contains randomly distributed Coulomb-type defects. The possibility to choose the combinations of diffraction conditions optimal for characterizing defects of several types by accounting for dynamical effects in the integrated coherent and diffuse scattering intensities, i.e. primary extinction and anomalous absorption, has been analysed based on the statistical dynamical theory of X-ray diffraction by imperfect crystals. The measured integrated reflectivity dependencies of the imperfect silicon crystal on azimuthal angle were fitted to determine the diffraction parameters characterizing defects in the sample using the proposed formulas in semi-dynamical and semi-kinematical approaches.

The role of gastric emptying in β-carotene absorption during simulated in vitro digestion

AbstractIntroductionThe availability of β-carotene from provitamin A rich foods in order to improve the provision of vitamin A in humans through food-based approaches is an important factor in mitigating micronutrient deficiencies. However, the extent of intestinal absorption (and subsequent availability of carotenoids to target tissues) is dependent on meal preparation, components of the meal and other intrinsic factors during gastro-intestinal (GI) digestion. Gastric emptying (GE), dictated by the caloric value of a meal, has been suggested as a critical component in determining β-carotene absorption. Indeed, dietary intake of high energy meals may just unravel the underlying factors associated with low uptake of dietary carotenoids during digestion. While several studies have reported the uptake of β-carotene as an individual pure compound under different digestive conditions(1), very few studies have assessed the effects of dietary carotenoids embedded in an energy dense meal, as would normally be consumed, on GI transit time and subsequent nutrient release.Materials and MethodsIn this study, we investigated the role of meal composition, particularly its caloric value, in modulating gastric emptying and thus the absorption of β-carotene. A step-by-step in vitro semi-dynamic model that simulates adult gastric digestion(2) was used on a prepared standard meal whose caloric value was estimated based on the Atwater system as described elsewhere with the assumption that the caloric density of the meal will assume a linear GE rate of 2kcal/min.ResultsPreliminary results indicate that, short transit times of 40 minutes, mimicking early GE, have the highest concentration (3.84 ± 0.014; Mean SD) and therefore, highest bioaccessibility (55.7%) compared to the longer transit time of 160 minutes (0.81 ± 0.002; Mean SD) and (11.8%) for β-carotene concentration and bioaccessibility from a standard meal, respectively.DiscussionThe results suggest that gastric behaviour of the food determines the kinetics of bioaccessibility that may not result in low β-carotene release and ultimately low bioaccessibility from the embedded matrix.

Optimization of Wastewater Treatment Plant Design using Process Dynamic Simulation: A Case Study from Kurdistan, Iraq

Satisfactory effluent characteristics are indispensable to evaluate the performance of any wastewater treatment plant (WWTP) design. Dynamic simulation software has a great role in pursuing this objective, in which an efficient and cost-effective design is constantly performed. In this study, a dynamic simulator sewage treatment operation analysis over time (STOAT) has been used under certain influent conditions to optimize design possibilities for modifying an existing primary WWTP College of Engineering Wastewater Treatment Plant (COEWWTP) at Erbil, Kurdistan, Iraq. The optimization was established on the basis of total suspended solids (TSS) and biochemical oxygen demand (BOD) characteristics in the effluent. Two alternative design schemes were proposed; trickling biofilter and aeration basin. In the dynamic simulation for the investigated design schemes, the predicted effluent profile showed that each of the existing and trickling biofilter processes has failed to correspond to the valid effluent limitation, whereas predicted results of the aeration basin exhibited an effluent profile that meets TSS and BOD allowable limits. Different simulation models have been implemented by STOAT to simulate treatment processes in studied design approaches: ASAL 1 model; BOD model; BOD semi-dynamic model; and SSED 1 model. This study offers an additional understanding of WWTP design and facilitates the application of dynamic simulators as tools for wastewater treatment development in Kurdistan.

Toward an accessible and robust in vitro approach to evaluate bacterial viability in the upper gastro-intestinal tract: A Gastro-Intestinal Digestive Simulator (GIDS) combined with alternative methods to plating

Abstract Since the viability throughout the human gastro-intestinal (GI) tract is a key metric to select new probiotics, we aimed to develop an evolutive and robust semi-dynamic model, named Gastro-Intestinal Digestive Simulator (GIDS), mimicking pH variations of the upper GI tract and based on the latest Infogest in vitro digestion protocol recommendations. We first tested the GIDS and its reproducibility by measuring, during in vitro digestion, the cultivability of bacterial strain contained in two marketed fermented milk products. Then, we used this model to assess inter- and intra-species variability among 16 bacterial strains from Bifidobacterium animalis, Bifidobacterium breve, and Lactobacillus paracasei species. Finally, we further explored the applicability of propidium monoazide-quantitative PCR and flow cytometry to GIDS samples. To summarize, our study showed that i) the GIDS model is reproducible and ii) the complementary methods to plating tested here are compatible with GI environments; providing insights that will guide future developments.

Development and validation of a new artificial gastric digestive system.

The stomach is a major digestive organ of the human body that plays a role in storing, mixing, reducing chylous particles and breaking down ingested foods. This study established a new artificial gastric digestive system (AGDS) with a human stomach shape and structure by a 3D digital technology. Two sets of symmetrical rollers and one set of contrary movement of the roller were used to simulate the peristalsis of the stomach, and a pH-stat workstation was applied to control the pH. The force, pepsin and gastric juice secretion, gastric emptying and pH changes of AGDS were tacked and validated. Besides, the digestion behavior of α-lactalbumin using AGDS model, static model and semi-dynamic model (pH and enzyme changes) were studied. The results showed that the hydrolysis and morphology of protein, peptide and amino acids accumulation obtained by AGDS were different from the static digestion and semi-dynamic digestion models, indicating pH and gastric motility had certain effect on protein hydrolysis, particularly in the pepsin activity changes at early stage of digestion. AGDS, verified by mechanical analysis and in vitro digestion experiments, indicated that it can provide α-LA protein solution with a true and reliable digestion profile in the stomach, and can be used as a potential dynamic gastric digestion model for the food development.

The simulated in vitro infant gastrointestinal digestion of droplets covered with milk fat globule membrane polar lipids concentrate

Milk fat globule membrane polar lipids (MPL) are increasingly used as the surface-active components for emulsions in many infant food products. However, the precise effect of the emulsifier MPL on the digestion of lipids during gastrointestinal digestion has not been elucidated. This study investigated the lipid digestion of droplets covered with MPL with different sizes in a simulated in vitro infant gastrointestinal digestion assay. The well-used surface-active component casein was used as a control. Four types of emulsions were formulated: small and large droplets covered with MPL concentrate (MPL-S and MPL-L, with volumetric means of 0.35 ± 0.01 and 4.04 ± 0.01 μm, respectively), and small and large droplets covered with casein (CN-S and CN-L, with volumetric means of 0.44 ± 0.01 and 4.09 ± 0.03 μm, respectively). The emulsions were subjected to in vitro gastrointestinal digestion using a semidynamic model mimicking infant digestion. Through the determination of particle size evolution, zeta-potential, and microstructure of emulsions, the lipid droplets covered with MPL were found to be more stable than that of the CN-S and CN-L during gastrointestinal digestion. Moreover, although CN-S and CN-L showed a higher initial lipolysis rate at the beginning of gastric digestion, droplets covered by MPL exhibited a significantly higher amount of free fatty acid release during later digestion. The amount of free fatty acid release of the emulsions in both gastric and intestinal digestion could be generally classified as MPL-S ≥ MPL-L > CN-S > CN-L. Our study highlights the crucial role of MPL in the efficient digestion of emulsions and brings new insight for the design of infant food products.

Research on the Dynamic Model of 2.5D Fluid Structure Interaction of Gravity Dam and Simulation of Seismic Stress Response

The seismic safety of the dam involves the safety of people’s life and property, and even affects the overall safety of the national economy. One of the key of technical issues in this subject is the more complete fluid-structure interaction(fsi) theory and the more accurate calculation method. In order to solve the problem of dynamic fluid-structure interaction in gravity dam, a 2.5d semi-dynamic theoretical model and a numerical solution method are established by using fluid slice method. The numerical experiment of seismic sress response is compared with three-dimensional model. The results show that the stress response of the 2.5d semi-dynamic model of gravity dam can well reflect the fluid-structure interaction behavior and effect of seismic gravity of concrete gravity dam.

The Potential of Metering Roundabouts: Influence in Transportation Externalities

Roundabouts are increasingly being used on busy arterial streets for traffic calming purposes. However, if one roundabout leg is near a distribution hub, for example, parking areas of shopping centers, the entry traffic volumes will be particularly high in peak hours. This paper investigated a partial-metering-based strategy to reduce traffic-related costs in a corridor. Specifically, the resulting traffic performance, energy, environmental, and exposure impacts associated with access roundabouts were studied in an urban commercial area, namely: (a) to characterize corridor operations in terms of link-specific travel time, fuel consumption, carbon dioxide and nitrogen oxides emissions, and noise costs; (b) to propose an optimization model to minimize these outputs; and (c) to demonstrate the model applicability under different traffic demand and directional splits combinations. Traffic, noise, and vehicle dynamics data were collected from a corridor with roundabouts and signalized intersections near a commercial area of Guimarães, Portugal. Microscopic traffic and emission modeling platforms were used to model traffic operations and estimate pollutant emissions, respectively. Traffic noise was estimated with a semi-dynamical model. Link-based cost functions were developed based on the integrated modeling structure. Lastly, a sequential quadratic programming-type approach was applied to find optimal timing settings. The benefit of the partial-metering system, in terms of costs, could be up to 13% with observed traffic volumes. The efficiency of the proposed system increased as entering traffic at the metered approaches increased (~7% less costs). The findings enable quantification of metering benefits near shopping areas.

Research on the Dynamic Model of 2.5D Fluid-Structure Interaction of Gravity Dam and Simulation of Seismic Displacement Response

The seismic safety of the dam involves the safety of people’s life and property, and even affects the overall safety of the national economy. One of the key of technical issues in this subject is the more complete fluid-structure interaction(fsi) theory and the more accurate calculation method. In order to solve the problem of dynamic fluid-structure interaction in gravity dam, a 2.5d semi-dynamic theoretical model and a numerical solution method are established by using fluid slice method. The numerical experiment of seismic displacement response is compared with three-dimensional model. The results show that the displacement response of the 2.5d semi-dynamic model of gravity dam can well reflect the fluid- structure interaction behavior and effect of seismic gravity of concrete gravity dam.